Timed perfectly, Casio watches that feature Atomic Timekeeping are just that. Several times a day they receive the official US government time via a time calibration signal from the atomic transmitter in Ft. Collins, CO. There is also no need to worry about changing your watch for Daylight Saving Time. Our atomic watches also feature a perpetual calendar. This eliminates the need to adjust your watch for calendar month to month inconsistencies and Leap Year. You truly will be on time, all the time.